FerronickelFerronickel matteMatte is produced pyrometallurgically by PT Vale IndonesiaIndonesia from lateritic ores. The ore is initially dried and calcined in rotary kilns, where Ni and Fe are partially reduced. Molten sulfur is added to the kiln, where it vaporizes and reacts with the metalsMetals in the calcineFerronickel calcine to produce sulfides. This sulfur-loaded calcine is then melted in Electric Arc furnacesElectric arc furnaces to produce crude nickel matteNickel matte, which is further refined in downstream converters. Little is known about the reaction kinetics of calcine with sulfur gas. This study investigates the effects of sulfur gas injection into calcine beds, focusing on sulfur fixation rates and maximum loading capacity of the calcine. Two types of crucibles were built (disk and pipe) to assess the overall and spatial effects of sulfur fixation. Results indicated that fixation rates increased with increasing sulfur boiling rates. Additionally, sulfur fixation was found to occur rapidly, with most of the fixation taking place near the injection port. The study also found that the sulfur-loading capacity exceeded the stoichiometric estimates based on Ni + Fe, consistent with historical data. Further studies are needed to fully characterize these high-sulfur-loaded calcines.